Genotoxic effects of the carbamate insecticide, methyomyl. II. In vivo studies with pure compound and the technical formulation, "Lannate 25".

The carbamate insecticide, methomyl, and the methomyl-containing technical formulation, "Lannate 25", were tested for the induction of DNA damage in vivo. Swiss CD1 mice were treated intraperitoneally with test substances and the following tests were performed: alkaline elution of liver and kidney DNA, 8-hydroxyguanosine detection in liver DNA, and 32P-postlabelling analysis of DNA adducts in liver DNA. The clastogenic activity of the two pesticide preparations was also evaluated as micronucleus frequency in bone marrow. No DNA adducts were detected in liver DNA of mice treated with pure methomyl, while a dose-related increase in DNA adducts was found in Lannate 25-treated animals. All other tests were positive with both methomyl and Lannate 25. A summary of genotoxic activity of methomyl is also presented. The hypothesis that the observed genotoxic effects of methomyl are induced indirectly, through formation of active oxygen species, is discussed.